Fix: null definitions and failing tests

[davidsedmancoxautomotive]

If a message is null it was applying "{}". This was giving an error of: 'invalid message definition for rpc style binding'. This is because in the soap client module the input.parts is null but the args = {}. See the following:

if ((style === 'rpc') && ((input.parts || input.name === 'element') || args === null)) {
            assert.ok(!style || style === 'rpc', 'invalid message definition for document style binding');
            message = this.wsdl.objectToRpcXML(name, args, alias, ns, (input.name !== 'element'));
            (method.inputSoap === 'encoded') && (encoding = 'soap:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" ');
        }
        else {
            assert.ok(!style || style === 'document', 'invalid message definition for rpc style binding');
            // pass `input.$lookupType` if `input.$type` could not be found
            message = this.wsdl.objectToDocumentXML(input.$name, args, input.targetNSAlias, input.targetNamespace, (input.$type || input.$lookupType));
        }

This fixes the issue.
Also two tests were broken.

[icholy]

Missing return type.